This invention relates to dynamoelectric machines and particularly to means for retention of coils in a core thereof.
In relatively large dynamoelectric machines means are required to secure the coils in the stator (sometimes the rotor as well) to avoid excessive vibration. In the past it has been the usual practice to use as coil retaining elements a side filler driven between the coil and the adjacent slot wall, slot fillers above the coil at the slot opening and, over the slot fillers, a slot wedge. The slot wedge is normally configured to be driven in notches or grooves at the opening of the slot to prevent any radial movement of the wedge.
Variously configured wedges have been used or disclosed in the past. Among them is a locking wedge disclosed in U.S. Pat. No. 3,740,601, June 19, 1973 by R. L. Amasino and P. S. Johrde. In accordance with this patent, a slot wedge of relatively rigid insulating material is made to be resilient and compressible at one end, as by providing at that end one or more longitudinal grooves extending a short distance from the end. Also at that end are laterally extending projections to give the slot wedge a normal dimension, when uncompressed, that is oversized in relation to the core slot dimension. Upon compression of this end of the slot wedge, the wedge can be inserted in the slot and driven through the first pack of laminations. When the compressed end of the slot wedge emerges from the first pack it expands to normal size with the projections locking into the first vent duct in the core. This effectively retains the slot wedges in place. The referred to patent also discloses use of a flexible strip of material on the outside coil surface over which one or more slot fillers are placed with the tape folded over the ends of the slot fillers and fixed in place by being held between the referred to locking wedge and the adjacent slot wedge of an interior core pack. This arrangement has been successfully employed, but difficulty remains in providing the locking wedge with sufficient resiliency so that it can be readily driven into the core pack and still securely retain the coils and other elements. The grooves or slots providing the resiliency of the oversized end may also weaken the assembly.